an X-ray of knee will solve ur problem. the local symptoms are usually same in a minor fracture
or a ligament injury
. only an expert can tell u after full examination, even sometimes he can't. a fracture will be easily seen in x-ray, other wise it will be considered as a ligament injury. MRI
is best investigation to look for muscles or ligaments.
by reading ur history i may suggest that it may be a ligament injury, but u should do rest, instead of walking, will help u in healing. getting an x ray
done is of no harm, along with an opinion with orthopaedician.