Hi

There won't be any consequences,  it's just that the students who've done BCA would have more knowledge related to computers than you and also BCA is application based course so they'll aslo have more industry knowledge. While Mathematics honors is more of a theoretical subject and also not related to computers. So you'll have to buckle up.

If we talk about eligibility,  then you're absolutely eligible to pursue MCA after Mathematics honors its a good option and taken up by many students who want to take corporate jobs in MNCs.

Hope this helps!

All the Best!