I have had tendonitis and tendonosis for years due to a reaction to antibiotics. The best pain relief I had was a topical 2.5% Menthol gel. I used it long term without apparent side effects. I get it at a 99 cent store so it is inexpensive. I prefer to avoid aspirin for regular use.
It is "Family Circle Muscle & Joint vanishing scent gel". It has no smell and is absorbed into the skin without a residue.