My longest ever run

So I'm back in my new house and decide I'll go out for a nice big run. My quad muscle is feeling much better and I'm feeling pretty strong. I set off and sort of know which way I'm going to go. I run down towards Eastrop Park which is about a mile. I continue on and feel really good as I hit the 3 mile mark. I'm now running over by Old Basing and I decide to cut up through Chineham. I run past my Mums house and at this exact moment my left ankle starts to ache a bit. I ignore and continue on through Popley and up towards our house.

I finish the run in 1 hour 1 min and it's a 11.6k run (7.2 miles). Really happy with that and I certainly didn't run it fast, I get a new PB of 10k in 51 mins 23. The only problem is my ankle is now aching, what have I done? Silly boy! Will I ever learn? I go from running regular 7 and 8k runs to a 12k run.. I think I have pulled a muscle.