Hello, I am glad to answer your dental question. The dark area indicates a change in the enamel and with a hole would be decay. Decay needs to be removed or continues to increase and reaches the nerve inside the tooth. Your sensitivity is expected when the protective enamel coating has been damaged. You may be able to fill the tooth if the decay has not affected the nerve chamber. Some sensitivity to sweets and cold often can be treated with a filling. Filling material is usually of a tooth colored composite. Other material choices include amalgam and if a larger section of the tooth needs replacement, then porcelain or a gold alloy should be considered. Once hot sensitivity and sharp pain become more prominent, you most likely have bacteria causing an abscess and will require a root canal or extraction. Sometimes only a very small hole is visible to the eye, but much destruction of the underneath layer has occurred. The sooner this tooth is evaluated, the better chance for a restoration such as a filling. Your dentist will need an xray to evaluate the tooth and suggest your treatment options. Symptoms such as throbbing, swelling, a bubble on the gum or fracture suggest a greater chance of an infection. Avoid chewing on the tooth and keep the area as clean as possible. Schedule your dental visit as soon as possible. I cannot provide a name of a dentist in your area. You may ask your general physician for a recommendation. You can contact your local government agency for a list of licensed dentists or locate a dental school which has a clinic or request a referral. Thank you for your inquiry. I hope you will be able to schedule an appointment soon.