Had a blood test 2 days ago. immediately bruised and had a lump. there is a still a lump and the bruise is now about 2 inch. another bruise developed last night. its kind of tender but not as painful as in beginning. i m a recent gastric bypass patient ive never had any problems like this in the past. the girl told me she hit scar tissue which is crazy since i haven t had a lot of blood work in past.