Please : what is the strongest over the counter painkiller for painful shoulder?

It’s great to have this website when you really need it. My right shoulder began hurting pretty badly Saturday night around 4am and continues. It could be bursitis or, as I think, tension. I can’t sleep well due to this so I’m tired at the same time I have this pain. What is the best pain reliever? Prescriptions are out. I have heavy groceries to lift but I won’t attempt doing it with this illness.TIA !!