Honestly this is my first cycle with Deca as well but I have not had that problem and I spread my injections all over my body. Today for instance I threw in 2 cc's of Deca and 4 cc's of Test E. I pinned 1 cc in each bicep of the deca. Then 1 cc in each shoulder of the test e and another 1 cc per tricep. In a few days I'll pin 1 cc split up between quads and 2 cc's of test e, one in each calf. I spread it out because when I attempted to put in 2 cc's into one muscle group I could barely walk. I have found that by spreading the injections it definitely cuts down on the pain. Maybe this will help. Is it possible that you are injecting too much into one area? How much are you pinning?

Mate bruising comes form bleeding under the skin. So it could be ruptured capillaries or the like. Don't worry bro

Are the spots you injecting in "virgin muscle" meaning never been pinned in that area? Usually I don't pin my glutes but started again after a while and i have just one bruise.