Hard Lump With Blood Cloth With Oozing Liquid. Had Wound With Blood Under It Post Accident. Cause Of Lump?

I was involed in a car accident 23 years ago. On my top left inner thigh it formed a hard lump which started pull when I walked and the vien where bursting around it. I had it remored this year in May. When I went back for a cheak -up the doctor told me that I had blood under wound and that I must put an ice pack on it. That night the wond starting leaking a clear bloody liquid out of the wound. I phoned him the next day to tell him and he told me to put a tight bandage round it. We went on holiday but was changing the brandage all the time as it was getting wet with this bloody liquid. I after the 4th day I told my husband we needed to get back home so that I can go and see the doctor. I phoned the doctor but it was along weekend and he told me to go hosipal, my house docter was on duty and had to re -open the wound as it had cause a blood clot. He cleaned it out and re - stiched it. For about for week I need to keep on going to him to have it drain. It now has formed a larger hard lump. Please could tell me if you know why this has happened