Hi, i'm having pain/stiffness on the right side of my lower back. i struggle to stand up straight after sitting down since yesterday. should i see a doctor?

Muscle spasm: Sharp pain in the lower back is typically a muscle spasm. Apply alternating Ice and Heat for 10 min each, take some Ibuprofen every 6 hours, and lie flat on the couch or even the floor to give back muscles rest and support. Once you can move easier, do stretches as detailed at https://www.healthline.com/nutrition/stretches-for-lower-back-pain#1 for prevention and relief.

Lumbar strain: Although information provided is limited, your pattern might suggest facet impingement or sacroiliac dysfnctn. You could try sitting in a warm tub of water, and take OTC NSAID'S, but if lasts longer than a few days, consult with your doctor. An osteopathic physician could be highly beneficial. A sacroiliac belt might help temporarily, but not permanently.