Odd Lump in Mouth

Just now, I found an odd lump in my mouth, which was painless and I squashed it with ease and it didn't hurt what so ever, it literally just felt like it was a sac of air built up in my mouth, however, after I done this I tried to look into my mouth to find out what it looked like, it was just what looked like a spot after you burst it, however where I had popped it there was a little red hole. The lump is now flat and resting on my Gum, when you look at it all you can see is a little red mark that looks like you've bit your gum and made it bleed.

Now the side of my mouth that the lump was at is feeling numb, I'm not sure if this is to do with the fact that I had pulled my mouth apart a lot to see the lump, though.

I didn't see it before I popped it.
If it helps to know, I'm 17.