I am pretty sure you cracked LCD. I used to have a lot of this issue as well. Sometime iPhone LCD didn't show cracked right a way.
- for iPhone, better remove polarize most of the time. for me i replace polarize for almost every time. iPhone 5/5s LCD can't handle too many pressure. so try to take time and don't give too many pressure when you clean up.
There is polarize glue remover (8222 250ml Polarizing film remover) but can't buy anywhere in US at the moment. Most people use blade.
I would say 80% LCD cracked when you take frame off from the phone. (for 6 and above model)