Uneven pupil sizes can arise from a whole bunch of things. For example, if you have adie syndrome, you would most likely have uneven pupils and some difficulties with light and reading. Adie syndrome is very easily fixed, usually with a pair of glasses and causes no threat to your health. Your pupils can also be different sizes from things like head traumas, eyedrops, or because of some drug or chemical in your body so it's very hard to tell. 

It's worth going to a specialist and having them rule out conditions so you know it's not something serious/ whether or not you have to treat it