blood blister

from The Century Dictionary.

• noun An effusion of blood-stained serum beneath the epidermis, forming a blister-like elevation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A blister filled with blood, usually caused by a sharp pinch to the skin.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun blister containing blood or bloody serum usually caused by an injury