I had a kenalog injection after 7 months of my BBL. Can this create a hole on my buttocks or Reduce the fat? (Photo)

   Steroid injections may cause fat loss and skin thinning, but this does not happen to everyone or every time.

Yes!   This is a fairly common side affect of steroid injections.   It doesn't happen to everyone, but it can happen.   But if you need it for your Asthma, then you need it!  You could possible ask for it in your arm next time though.  

Kenalog can atrophy the tissue where it is injected and can also change the pigment of the skin overlying where it was injected if it is injected more superficially. This does not happen to everyone but definitely is a known thing.