Felt painful twinge excercising 8 weeks after ACL replacement

Hi all, just a quick question:

I had an ACL replacement op 8 weeks ago and was recovering nicely, exercising my knee regularly and attending physio. Yesterday whilst at the gym I was doing some lunges (as instructed by my physio) and felt a sharp pain in my knee (the same pain I felt whenever I twisted my knee previous to the operation). The pain disappeared as quickly as it came but since then I've been worried that I've damaged the graft in some way. My knee feels a bit sore too.

I won't be seeing my consultant for a month and my next physio is mid week next week.

Any ideas? Thanks Fletch:)