Colourless bump on knee overnight

Hello, I'm new here and not sure if this is the right topic. This morning, i woke up to find a painless, colourless bump on the outside of my left knee, above the tibia. It is 4cm long, 1 cm wide and about 1 mm tall. I have not had any recent injuries but I had been on a long hike, which tried out my legs a couple of days ago. I am a 13 year old boy , and had never experienced this. Could this be cyst? or a cancerous tumor? When my leg is fully bent, it sticks out more and when its extended it seems to sink in. it seems to be swollen (ish) and when you press on it, it feels less pain than other unaffected areas. Could this may have been caused by sleeping on it? or is this a malignant cancer tumor? Please help :(

[CookieStealer]

yup. defiantly wrong topic.