Root canal usually costs from 1500-4000rs. Visit a dentist.

show an x-ray of d tooth

Your description is slightly vague to arrive at a rational diagnosis of your problem. Please post a clinical picture of the tooth and an x-ray if possible for a better understanding and a better suggestion. Otherwise the best way is to visit a dentist and get the case evaluated properly. The cost of any treatment will vary from dentist to dentist and when it is about a cap, it can range from 1000 rupees to 25000 rupees depending upon the type of cap and the warranty certificate come provided by the lab. Regards.