You can participate but since you did not get in CSAB Round 1, chances of getting a seat in the same institute in CSAB Round 2, seem bleak. However it is your decision. Some institutes like your Home State NIT or BIT Mesra and a couple of more GFTIs might have even lower cutoffs in CSAB, but not many other Top NITs.

You should hence continue with the seat you got in JOSAA and focus on your studies ahead.