If you do not want to take this to the hospital, it is perfectly fine. However, it is advisable for you to get a medical opinion on what this could possibly be. You should be aware that a white spot or any other kind of discoloration of the skin can indicate a vast variety of skin problems starting from mild ones such as a sun allergy to really serious ones such as skin cancer. It is better that you do not neglect this right now and get a medical opinion to begin with. Chances of a speedy recovery as well as a proper course of remedial measures will always be to your advantage rather than anything you might try to figure out on your own. The first thing you need to determine is if your back is constantly exposed to the sun. If this is the case, you could very well be suffering from a rare allergy to the sun's rays. There is no known cure for this particular ailment. About all you can do is control your exposure to sunlight and use a few simple preventive measures such as a sun screen lotion. Just ensure that you use a lotion that has a sun protection factor (SPF) of more than 30. This will drastically reduce your exposure and will minimize the damage done by the sun's harmful UV rays. Make sure that your sunscreen lotion has both UVA asd UVB filters for maximum protection. The other thing you must do is try and keep the skin on your back covered as much as you possibly can. This will also make a very big difference. Simply not exposing your skin to the sun can be extremely useful in avoiding the negative effect of the sun's rays. You should also try as much as possible to avoid going out in the sun during the afternoons. This is the time when the rays of the sun are at their strongest and should be totally avoided. So you are better off staying indoors between about 11 am to about 4 pm As this is the typical danger zone. However, if you continue to follow these measures for a couple of weeks and still do not see any signs that the white spot has stopped growing or is receding in size, you are once again advised to consult a physician. It is also possible that you may be suffering from the beginnings of leucoderma, particularly if you have a family history of this pigmentation disorder.
answered by G R