Anything is possible but I doubt it... Pain is usually itching or near the nipple most of the time.
500 is very low and enanthate takes a good 2-5 weeks to truly kick in..
At the same time, anything is possible, so if you are concerned, start Nolva @40mgs for the first week and then run it for 20mgs until your arimidex arrives.
Gyno is very unlikely on 500mgs unless you have existing gyno and/or predisposed to it..
If so, then you better run arimidex the whole time and get some Dostinex @ .5mgs E3d while you are at it..better safe then sorry.
Are you sure it's not a muscle tear or injury?