I did the same thing once. Pulled a hammy playing softball. Put those re-useable blue ice-packs on it, and every time it didn't feel cold anymore, I got a new one. After about 4 or 5 hours I stopped.
Next morning, I woke up with a huge red, sore spot amazingly similar is size and shape to the ice packs.
To make things worse, my mother in law gave me some of those "healing magnets" and I taped them on - about a few hours before the whole thing BLISTERED!
It oozed for a few days, and it was such a pain to keep it wrapped, given the tapering shape of the upper leg, that I eventually went and bought some super-absorbant maxi-pads with the adhesive, and stuck them to the inside of my pants.
I still haven't lived that one down yet with my family.