Race for life Hyde Park July

Hi, I know it is a long shot but I was wondering if anyone else on here is signed up for the 5K run in Hyde Park, London for Cancer Research? I signed up yesterday and I am terrified I can't even run right now, at all. I have hurt my knee and so have been swimming 3 times a week for 40 -50 mins and I also take my dog for a half hour walk every day. The pain in my knee has now stopped and I know I need to start running again but I am so afraid of hurting my knee again. I have this idea that if I can lose some more weight then it will be easier on my knee but I know I am running out of time, the race is at the end of July. Anyway if there is anyone else out there training for a 5K run or has delt with knee problems and running it would be great to hear from you. Thanks