I had this sebaceous cyst on my right cheek (face) for 3 yrs. Had steroid injected 2 times. It got smaller but will the cyst sac still be there?

Yes. Typically, unless the wall of the cyst is removed, the cyst tends to recur.
Yes it will! And that means it could very likely recur. Steroid injections seem like a good idea to reduce inflammation and soften scar tissue, but too aggressive and you get a divot (big dent). Now what? Have it surgically excised including sac and it's gone with the tiniest scar possible. Call a plastic surgeon, not a dermatologist! please, no more steroids either!