Is pain on the inside ofmy knee a type of MCL sprain or could it be something else?

Possibly. Medial sided knee pain typically can be caused by a medial meniscal tear (shock absorber), mcl sprain, or arthritis. If you have sustained a recent traumatic event, any of these could be the cause of your discomfort.
Have it evaluated. Possible cause of your pain may include sprain, bursitis, fracture, contusion, neuritis, but of course there are a multitude of other possibilities. Get the feet inspected by a professional to determine the cause of the problem, as treatment varies depending on the diagnosis.