What Causes Swelling And Pain In Knee Caused After Injury?

About a week ago I had an accident and injured my knee. I was able to walk on it and it just felt sore and stiff, like muscles after a workout. There was some swelling but I ve been icing it and the swelling has gone down for the most part. Now there is just some minor swelling on the inside of my knee, next to my knee cap and after standing or walking I also notice swelling in my inside ankle area. The pain is more of an ache now, amd seems to travel from the inside front of my knee and down my shin, and into my foot area. I have a hard time fully extending my leg, it causes pain and soreness. I had minor bruising to the front and back of my knee. My biggest concern is a small, somewhat movable lump on the back of my knee. It s in the middle back of my knee and doesn t hurt, but it wasn t there before the injury. It s not really hard or hot, and is a little larger then a pea. Could it be a blood clot?