I am wondering whether I  have pericoronitis or maybe another problem? I don’t know whether it’s a coincidence or not, but it's  only come on recently, and I have  just recently started using a Y Active Plate Expander. But I first noticed a around a week a go that I started getting some soreness next to my bottom left wisdom tooth every time I eaten or brushed my teeth. I checked in the mirror only just today and noticed the area looks fine, until I lift up the tissue that is around the tooth where I can see some redness in the corner. I am thinking it might  be pericoronitis, but I am not getting all the symptoms stated, it's only when I brush or eat on that area that it feels sore. It feels fine unless I do these two things. 

I have tried to take a video of the affected area, sorry if it's a bit gross:

 https://imgur.com/a/tKA5iAL 

You can see if I move the tissue off the wisdom tooth , there is some redness and it bleeds a bit if I pull a bit too much.

Would be grateful for any advice. I am really trying to avoid the dentist because extractions are the last thing I want.