Hello,

for now, one paper of 12th board is still pending. Board is planning for it. They will plan about supplementary exam after results comes out. For now, no details is available. They will  decide and plan so that no student will face any issue for higher studies.

if your board exam is completed then prepare for papers which you want to appear supplementary. Meanwhile, you will get your results. if after result you feel like you should appear for it then go for it.

for more information. ask your college authority.

Hope it helps!