Talk to General Physician on Pain In Knee While Walking And Getting Up From Flour

few days back I went on a picnic and when I came back I felt pain in muscles and knee for few days (may be because of swimming and hard work) but my entire body is fine now except knees. I can't walk for long, cant get up from flour easily. veins at the back of knee seems weird to me.. do I need to see a physician for some treatment or it will heal by its own. attached are the pictures of backside of knee.