As long as you use the word Doctor or initials Dr. in such way that it's clear that it is part of a business name and not that you are claiming to be a Dr. or have a Ph.D, you are fine. You can call your business "Computer Doctor" or "Tech Doctor" or anything like that; you can refer to yourself as "John Doe, the Computer Doctor," or similar things; what you can't do is anything like "Doctor John Doe," or "Dr. John Doe," etc. since that usage implies you have the degree.