Pulled lower back. Working out again?

I pulled my lower back on the right side just above buttocks while lifting, had no pain while it was pulled, I had no swelling or tenderness, had no pain while bending forward and sideways just had spasm while bending sideways towards left side while sitting. I stopped lifting, had occasional spasms while doing certain movements for a few days and then lower back got a little stiff, did MRI and it said no extrusion and no protrusion but mild Annular bulges at L4-L5 and L5-S1 with partial flattening of the thecal sac and a minimal narrowing of the neural foremina but no neural compromise. It's been around a month and I feel almost heald now, lower back just feel a little stiff if I sit for an hour or long. Was it a muscle problem or the bulges caused it?... Should I start working out again?