It won’t matter much if you pin it on your last dose day or wait a day or two. Make sure to pin it SubQ. HCG is supposed to be pinned that way.
2 weeks is really pretty early to start PCT. You are taking 500 mg/wk. Half life is about one week for Test E. Your natural levels (before cycling) are probably around what 100 mg of Test E a week would get you. Additionally, your HTPA is going to be hesitant to restart if your exogenous Test level is higher than your endogenous Test level would normally be. You would have these levels based upon exponential decay…
One week after pin equivalent dose: 250 mg
Two weeks after pin equivalent dose: 125 mg
Three weeks after pin equivalent dose: 62.5 mg
Two weeks after pin equivalent dose: 31.25 mg
After two weeks you can see you will likely be above natural production. I encourage you to wait one more week if you want your PCT to be more effective.