about a week ago I suddenly got a bubble under my skin just beneath my knee, where my shin starts. it looks bruised but I have had no injury to it. then today, I started to get a swelling bubble in the roof of my mouth. it is not painful, but uncomfortable. It feels like there is fluild inside it, but I have not had a burn or injury to my mouth either. Also there is some discoloration, like a bruise. any suggestions on what it could be?