Tip of my finger feels numb after playing guitar for years (also smoked a lot)?

Callus Formation. Your symptoms are likely due to callus formation - it is thickening of the skin in regions that receive repetitive use - like strumming a guitar. These areas do not have nerve endings and sensations may feel more dull then in rest of hand/fingers. Callus removal is usually done by salicyclic acid, or pumus stone. If that doesn't work, you can see a dermatologist.