There's really nothing that can be done for a blood blister except to leave it alone. You're not supposed to pop them; I know from experience that this only makes it more painful and takes longer to heal. I've gotten blood blisters from working with wood and getting my fingers pinched. The only thing I could do was try not to let anything touch/ hit it. After about a week the blood kind of dried up inside the blister and the skin hardened to become like a callous, then was easily peeled off. Because your blister is on the inside of the lip it may heal differently.