dear student

In case, you are not won’t satisfied with the allotted seats, can go for the second round of NEET Counselling.

you don't need to register again, but you can submit fresh choices of colleges. 

Candidates who did not register can freshly register and make choices.

visit the given link for more information about counselling process

https://medicine.careers360.com/articles/neet-counselling

hope this helps

All the best!!!