2 days ago the tip of my tongue felt sore, that went away. Today the right side of my tongue feels numb. Why?

Unknown . Difficult to give you answer without examination. Will see what happens next, gargle the moth with mouthwash. If no improvement you should see a doctor. .
Tongue numbness. High probability it is the aphthous stomatitis, once believed to be caused by a herpetic virus. In reality we have no clear cause but can be confused with a herpetic infection if the stomatitis is extensive with big vesicles and very painful. Some immunodeficiencies are implicated also. If longer than 2 weeks it has to be checked by a physician and blood work ordered. (Canker sore)4.