I did the same thing a couple of weeks post ACL reconstruction (using hamstring tendon). I tried to remove my shoes using my feet when I heard a pop and immediate pain in my posterior mid thigh area. I knew straight away that it was torn and it did hinder my recovery as hamstring's are weakened by the surgery.

I used the PRICE technique (prevention, rest, ice, compression and elevation) straight away.

I started physio at 10 days post op, so you should see a physio asap so they can help manage your current injury and rehabilitate your new ACL. Hopefully this will aid the success of your op.