Seems like I've a minor strain of my lateral collateral ligament.

Can anyone recommend a specific post ride stretching exercise to help?

Trying to find mine... Where is it?

relative REST. Stretching will not help a ligament injury. Time will.

Lateral Collateral Ligament is on the outside of the knee. I'd see a MD or specialist about it toute-suite. An inflamed LCL isn't anything to go ignoring. The LCL is usually injured through a violent movement (football hit) or repetitive motion. I'm guessing that you've got bike fit issues if you're having the problem.

Post-ride (assuming it is an LCL strain), I'd ice it for 20 minutes.

Are you sure it's your LCL? Common things being common, chances are you have soreness of your Iliotibial band (a muscle+tendon which can respond to stretching). You can look up stretches on google. Also, you can try to increase your float by using the appropriate cleat or adjusting your pedal if it's an option, make sure your saddle height is correct, keep your cadence up when it's sore, and stretch twice per day, as well as before and after your rides. These are the measures that really helped me.

Nope, I'm not sure, it's self diagnosis. It's not a pain, more of a strain (feels stiff) and doesn't seem to impact on my riding. I feel it the day(s) after a long ride particularly if I've been up a few hills (out the saddle).

It doesn't restrict my daily movement it's one of those niggling little things that are hard to narrow down to a specify spot. I've tried rubbing, squeezing the location but can't induce the discomfort!

It's my right leg, behind the knee and located on the outside of the knee, so it could be my Iliotibial band.

Ive had ACL re-constructive surgery , ligament issues are not something to play around with if it really hurts see a doc and get a good diagnosis

Sounds more like your IT band or, since it's behind the knee, biceps femoris tendon. In both of those cases, regularly using a foam roller helped me a lot.

If it gets bad, you probably want to see a physician or a PT. I think PT is mostly quackery, but they can at least help you diagnose the issue.

^^ THIS^^

Why would you want to risk a major injury by using BF.

Go to your Dr. and get it checked out.

Your ligaments connect bone to bone, whereas tendons connect muscle to bone. Stiffness would correspond to a tendon injury and ligament damage would result in problems with stabilization. I tore my MCL (opposite side of the LCL) in a football injury, and my leg would swing outward due to there not being a ligament to hold it straight. If it were a LCL injury, your leg would feel as if it were constantly "toe-ing in". I would definitely ice it up and see if that takes some inflammation out of the knee area. Then see a doc if it feels any worse.. Good luck and heal up soon!