Just joined for 2018

Hi everyone, name is John Montgomery, just started road cycling again last year-bought my first road bike since 1964........
I have been out on a couple of club Sunday runs on the short course-enjoyed it but not the pain in the tendons at the back of my left knee-any suggestions?
I shall need to get a lot fitter before I try the TT course-I ride the course as part of my local route-best time so far from extrapolation from my Garmin is 42 minutes......
See you out there
John.