hi mohini,

first thing is that you can go to the block of ur region and can get it updated 

• if you come under obc they will reattest it and your certificate will work
• but if you doesnt come under obc and couldnt produce certificate at the time of admission then you are considered as general student
• but if you are taking seat as obc means in obc quota then you need to show the obc certificate or else your seat may get cancel.

better you ask your college about it now only,

hope this hel[ps you out and you can ask more queries if needed.

have a great future ahead