No, you should not use Tretinoin 0.025% cream inside your mouth. This product is strictly formulated for use on the outer skin. The inactive ingredients in this cream are not safe to swallow and can cause severe irritation, burning, and damage to the delicate lining of your mouth. While topical retinoids are sometimes used to treat oral lichen planus, they must be in specialized formulations designed specifically for oral mucosal use. Please consult your doctor or dentist, who can prescribe safe and effective treatments designed for the mouth, such as targeted oral steroid ointments.