It would be good to see a picture before contact lens use. In some people who use contact lens for many years the lids may droop. Unusual after only 11 years, but possible. Especially if you were a little low to begin. The astigmatism was probably always there and is...
Yes, this is a possibility from correction of the affected eye. You may have to have ptosis repair on the opposite eye, but I would give it some more time to see how things respond with the swelling subsiding.
The answer depends if the droopiness is causing problems right now (either blocking vision or causing head to move back). You have to see a pediatric ophthalmologist along with an oculoplastic specialist. If it is not causing problem, then best to wait until teenage years.