Hello darpan,
If your percentage is greater than 75% in your 12th boards you can eligible for most of the engineering college. With 89% in physics and maths you are eligible for BSC in CSE. You can easily get admission in your desired college with computer science branch. Only for top tier colleges such as DU your percentage should be in the range of 94-98% to get admission. You can also write various entrance test for colleges to secure a seat and get admission.