If it doesn't hurt and there's no other symptoms going on I don't think I'd be concerned, imo.

I have bruises all over my body that I don't know how I got and sometimes they are so big I don't get it. I did know that with fibro I tend to walk into things and I'm also iron deficient; however, sometimes they don't make sense. Right now my left forearm looks like I was in a gang fight - strange.

If you are concerned though - you could call your doc. and ask.

Tranquility