What is there a squishy lump on the outside of my ankle?

I am a normal, healthy 24-year-old female. Yesterday I noticed I have a squishy bump on the bottom of my ankle.THREE days ago, I stepped on my son's toy and kindda threw myself forward to the ground because it hurt so much. It just hurt the bottom of my foot, not my ankle. I didn't roll my ankle either. Yesterday, a day after, it started to hurt a bit when I walked. That is why I was examining my ankle. This lump is squisy, and when I push it side to side it feels almost like there is fluid in there. It's hard to tell. I can feel the tendons in there too. They feel stringy. I'm not sure if it's just swelling or what. As far as I know, I didn't hurt my ankle 3 days ago in my "accident", but it happened so fast that maybe I did. I also must say that 2 years ago I rolled the same ankle, and suffered an extremely bad and painful sprain. It took about 6 months for it to completely heal. I am wondering if the lump is from that sprain and I never noticed it until just now when my ankle is hurting. Since I noticed it, my ankle has been wrapped with a brace and I am taking Motrin. Ther is no improvement. My real concern is if the squishy lump will heal itself or if I need to go to the doctor to have something done about it? Als if the lump is a result of a hurt ankle, or if my hurt ankle is from the lump? Thank you so much for your time!!