Get to Physiotherapy NOW. Ask your GP if there's a physiotherapy clinic attached to the practice OR get referred to your local nearest physio. DO NOT WAIT.
Apart from anything else - the doc may be wrong, it could be ligament or something else. If you're unsure at all - get to a hospital (A & E) and get them to look at it.
I had a ligament injury to my knee about 3 years ago.. I held off for a couple of months and it got worse and worse.
Went to local A & E (ER for US-ers) they put a sort of splint thing on it... the upshot was that the upper leg muscles completely wasted through my "favouring" the leg. Ended up with crutches and sticks. The physio I eventually saw was brilliant, but she stressed that they'd rather see someone in the first instance, not three months later once there was some real damage to put right.
Can't emphasise enough how important it is to get help sooner rather than later. My leg's Ok now but it took months to make right the damage caused by not getting the right treatment ASAP.
All the best...