Frozen shoulder by any chance?
How long the steroid injection will effect your BG's is difficult to say, as it can be dependant on dose used and how your body responds to the steroid!
Even though you'll T2, I would discuss with your doctor to ensure that you have a good supply of test strips so that you can monitor your blood glucose carefully, also an action plan if your blood glucose rises too much and starts to become unacceptable levels, as a small increase over a short period of time isn't going to pose any problems over a long period of time, but a large increase will need addressing in the short term..
I'm a T1, but after looking at the effectiveness of steroid injection for frozen shoulder, decided not to go ahead.