Magic Tricks

Should you be concerned?
Maybe...but not necessarily about damaging the inside of the phone using the gimmick. That isn't likely to happen at all.
However, you should be prudent with your concern about the gimmick itself breaking and the phone, whether yours or borrowed, hits the ground and needs repair/replacing.
I went to Walmart and asked to have one of there old, dummy display phones for when I use this gimmick.