Hi Pavan, 

Your CAT score is valid for one year. You can take admission for the academic year 2018-20 in any MBA college/institute which accepts CAT score. However, I believe you wish to pursue distance MBA since you mentioned 'online MBA course'. Online MBA courses are offered in distance mode by many open universities. You can try for online MBA in the following institutes:

1.  ICFAI

2.  Symbiosis, Pune

3.  IGNOU

4.  Amity University, UP

5.  Annamalai University, TN and

6.  Sikkim Manipal University

With a score of 81.4 percentile you can get admission in a decent private college, so why not go for that! Here are the colleges for your consideration.

1. Institute for Financial Management and Research (IFMR)
2. TAPMI 
3. BIM, Trichy 
4. LIBA, Chennai
5. XIME, Bengaluru 
6. NIRMA