The plug for the laptop is slowly changing colour, is it still safe to use until I get a new one

So, right now my charger plug, that connects into the extension cord is slowly changing colour and it looks like it has small bumps, I can’t really tell though.

Is it because i’m using an extension cord or is it something else?

I use an extension cord instead of the actual outlet because, the outlet is too far from where I’m situated with the laptop. I know I can move but there isn’t much room in my apartment to move furniture around.

I’ve never had this problem with my older laptop and that was also plugged into an extension cord, but it was one of the bigger multiple outlet ones, with the ability to turn it on or off.

I just want to know is it still safe to use until I get a new one, or do I need to change my extension cord?

Laptop is – Acer Spin5
Input – 100-240V-50-80hz 1.2A
Output- 19V-2.37A

Extension – 16 gauge calibre
Wire type: SPT-3
6’7”/6pi 7po(2m)
Length 0-50ft/pi(0-15m)
51-100ft/pi(16-30m)
Max.Amperage: 13-10
I got this extension cord at Canadian tire

Thank you

UPDATE:
I want to thank everyone for there suggestions as to what the problem could be. Sorry for not getting back quick enough it’s been an insane month.
When I first posted this, I decided I would leave my laptop alone until I got a new extension cord and new plug. If anyone has any recommendations on a new extensions cord, that would be greatly appreciated.

Before I continue into that, I do want to thank everyone here who is, at this point in time and when it all started, an essential worker. Really thank you so much for all that you’ve done!

So back to the plug; I got the extension cord, maybe a couple months after the laptop, and that was at the beginning of January 2018. So from what I could remember it started to change colour around the end of 2018-beginning of 2019.
It started small but slowly started to change over time. I suppose with being home now a lot more than before I’m really noticing it. The plug won’t heat up but, when I do pull it out of the ext. cord, it will be warm, not like warm-hot but cold-warm, if that makes sense?
Someone did suggest that it could be the extension cord, this has never happened other extension cords before, so I hope it’s only that.
Edit: Then again, I’ve plugged other things into the extension cord, like; my portable charger, hair dryer, stuff like that, and none of there prongs have ever started to change colour.

So about the laptop, it does heat up when it’s plugged in and I’m using it, but it’s always done that, since I first got it. I do put it down to let it rest for a couple hours until I’m back in again.

The outlets in the apartment are pretty old, maybe as old as me, I’m not sure? When I asked my parents they said that they don’t remember when the outlets were last changed. Some of the outlets I did notice are a lot stronger, most of them could handle objects that need to stay plugged in for a long time without causing a fire. Others have at this point become loose, so using them is a no go. Once I do get a new extension and plug, I’ll probably move into the living room.

Here’s the thing I would love to have them all replaced, but it would only give the new owners of the building more incentive to add onto the rent we already pay. Even if we had someone, not in a contract with the buildings, to come do it, they would still probably add onto our rent anyway. Trust me they’ll do that to just about anyone in the apartment, no matter what.

Thank you though for reading this, if you did get down here, again if you have any good extension cord recommendations, it would be appreciated. Also I think I’ll start using it again for a short while, I’m back to work (New Job!), so I think I would be ok to use it for 3hrs and then stop for about an hour or two and then go back? This is just until the new extension cord and charger come in.

I hope some of the new information on both the laptop and plug for it was helpful, if you do need more info just ask. Again thank you! I hope you and your families stay safe during this time!