Hi there, your case requires a subjective assessment done by a physiotherapist, as the description of your symptoms suggest anything between I-T band syndrome to a hamstring injury... your physiotherapist will perform some physical tests on you and conclude a diagnosis with proper rehab protocol... so please don't wait before you see a physiotherapist. .. hope this helps, feel free to contact for any doubt...

From limited discription you have given, Pain on sitting on ground and getting up from sitting position could be because of 2 most common things, 1- early hip arthritis or 2- hamstring muscle pull. If your pain increases on cross leg sitting also then probability of hip joint affection is more. You can show to physical therapist and get some pain relief and correct faulty alignment if there is any and recover and prevent further deterioration.