In the last month ive had muscle pain on my left leg, started on calf and ankle moved to back of the knee, was hard to walk/stand or seat for long. now the pain is gone but my leg keeps swelling up. what am i dealing with? should i get it check?

Absolutely see MD!: most commonly pulled muscle/tendons and strain, but depending on family history, smoking, medications/drugs, clotting disorders, etc what you describe can be from more serious underlying conditions e.g. clots in vessels, "cysts"/edema (fluid filling), even spine/nerve problems so see MD as soon as possible - emergent if red flags e.g. breathing difficulty, chest pain, fever.