First thing you should do if something feels off is a water change. Let us know what your water parameters are when you get them.
Lots of things can cause fish deaths, and the 2 deaths may or may not be related. The first one could well be the result of the injuries and stress you mention. The second? Any signs of disease or injury? Perhaps the fish was sick before you got him. What are the living conditions of the fish in the store you got him from?