If you have taken a niyam to stop eating mangoes after Ardra nakshatra, then you should not eat them after that time, even if they were bought earlier.

If you have not taken any such niyam, then this is not a universal Jain rule. In that case, the decision depends on your family or sect’s tradition.

In Jain practice, the safest and most disciplined path is:

• eat them before the niyam starts, or
• avoid eating them after it begins if you have already committed to that vow.

If you want, I can also explain why mangoes are often avoided after Ardra nakshatra in Jain tradition.