Some guys react BAD to sust and prop. I'm one of them. Advil, Aleve, Tylenol just don't do shit for that pain. You can rotate, massage it, inject before working out, bake it, warm it before injecting, pretend it doesn't hurt, have sex with Jessica Alba....
It won't matter. I know you aren't going to ditch the Sust, so a couple things that might make it tolerable. I would swith to Aleve and up your dose towards the prescription dose level. Take two tabs at a time - 440mg - 2x daily. Also, you can take Tylenol at the same time. The two will give you better relief than either alone. Don't mix NSAIDS (advil, aleve, asprin, etc). Tylenol is acetaminophen and can be taken with NSAIDS.
Secondly, you can cut it with sterile oil. You may need to split up the inject and do it in two sites rather than one, but you reduce the concentration of the prop and/or BA levels.
I hope that helps you. Oh yeah, and NSAIDS supposedly gain reduce gains or actually inhibit healing from any injury, but you are on cycle and I don't think the amount it hinders peoples recovery is as significant as it is made out to be. Furthermore when the pain is intense, it hinders everything you do.
Good luck.