4 months post op - worried about damage

Last night I tripped slightly and planted my operated leg to balance. I felt a little bit of pain at the time, nothing major, and carried on with my night. I woke up this morning with a very stiff knee with a little bit of swelling at the back and it is a bit painful to try to and bend it now. It’s been 24 hours since the incident now and it hasn’t gotten any worse but I’m still worried I might have done some damage particularly with the loss of ROM. Might I have done some serious damage or just a little bit of aggravation?