Welcoem to HCM!
After going through your question I can tell from my experince that you have a lock knee. you have had these episodes before but this time it is not getting better itself (which is the usual presentation) . it can be painful and there can be difficulty in bearing weight.
I would sincerely advice you to visit an orthopedician as it can cause further injury
to your knee.
from my clinical experince I can say that you should get an X ray
knee joint and may be an MRI
to checks the status of knee joint.
A pain killer and anti inflammatory drug like, aceclofenac
can help you till you see a doctor.
Hope you get well soon!
feel free to ask more queries.