I have had the following three things on my lip area in the past.

1. Canker sore - usually on the inside of my lip, facing the gums (hit
it while brushing) or on my inner cheek (bit it while chewing).  Hurts
like crazy for 2 weeks then gets better
2. Cold sore - usually on the outside of the lip (facing people) and
always in the same spot.  Tingles and looks like a clear blister.
3. Cracked/dry lips - after putting on lip balm and increasing my water
intake its better in a few days.

But this morning I looked and on the inside of my lip (facing the gums)
there was a "blood" blister.
I think thats the best way to describe it.
It was round, dark red/black.
Did not hurt, I actually thought it was a piece of chocolate from last
nights cake.
But I rubbed it and it did not go away.

I've never had anything like this before...what could have caused it?
Should I be concerned?

When I have gotten kicked in the mouth, it split my lip.
Or I would get a canker sore in a day or two, but I never saw anything
like this before.

This afternoon, I rubbed it again, and it started to bleed.
I just looked at it now (1:20am) and its gone....I guess I opened it
and the blood got drained?

Thanks