If it has disturbed you enough to come looking for ideas in a site like this then perhaps a visit to an orthopaedic specialist is not such a bad idea. With a user name like yours, I'm assuming you are in the UK which means maybe putting yourself at the mercies of the NHS

In the mean time, Plumb's advice to ice the knee is a good idea. Most of us here are more than familiar with the ritual of R.I.C.E. and are all aware of the need to reduce swelling at all costs. Look in any good sport's injury guide and you will see that it is always the first line of defence.
If you are in the UK and do not have private medical cover, you need to tell your GP to give you a referral to a knee specialist as soon as possible. We cannot offer anything other than wild guesses as to what maybe or may not be going on in your knee. Only a specialist who is "hands on" can give you a diagnosis and from there a pathway back to full functionality.
As I remember the Suffolk Punch is a rather large strong dray horse (having grown up on the Suffolk/Cambs border) as well as a very robust motor mower

. Or are you just an Ipswich Town supporter?

Sue

in southern Germany