Many times when hardware is used in surgery the end result is alot of pain afterwards. A good friend of mine stepped in a hole in a friends yard and pretty much had a crushing type injury to her ankle. Her ankle was a mess. But, she had an excellent surgeon and as far as the surgery went everything went fine. Two yrs postop the pain would not stop. End result was having the hardware removed before she felt any relief. Mind you, after the removal of hardware she still had pain but less. Trying to trick the body into accepting something that was not there originally is a very difficult at best.
No one here can say whether or not your dr missed anything. If you are thinking along those lines get yourself a second opinion. Get your surgery records and any others relating to this and see what another dr thinks. It never hurts to get a second opinion.
But again, remember what I said previously, no surgery is 100% pain free afterwards, especially involving bones and joints. That ankle will always be weak as a result of the trauma it sustained in this injury, surgery was simply to fix the problem and pain afterwards many times is part of the end result. Since your dr feels you have inflammation going on in there, that can be the culprit of the pain. The injection may settle all of this down-but at some point later on it may flare up again. No one can tell you for sure. Another thought is what kind of shoes you are now wearing after having this surgery, is there some way you may have twisted the ankle a little without realizing it at the time, the list could go on and on of what if.
When are you suppose to go back and see your dr? How long did he say it would take for the foot to settle down? How long has the pain been there, ever since surgery or what? Is the pain constant and how severe? Another thing to try is soaking your foot in warm Epsom Salts, alot of times that can help. Good luck. Susie