Hello, I hope you are doing well

If there is no option to change the category now, it would be almost impossible for to avail the benefit of PWD Quota. You will have to go through the entire process as an OBC Candidate because the category which you select during form filling is considered to be the final for the entire process.

You can still get the benefit of OBC quota, if you have work hard you shouldn't worry about reservations. All the best.

Hope this helps.