HELP PLSSS!

My son who is 5 months old sometimes has trouble pooping his doctor told me to give him apple juice. He hasn't pooped since Thursday so I gave him Apple juice today around 10-10:30 I then was getting his bottles ready to leave and as soon as I was about to pour the juice on his bottle I seen it had mold!!!! The first time I poured it I didn't see it had it I was just waking up and i wasn't paying attention & I feel really bad !! He only drank 1 1/2 oz of the juice what can I give him?? I called his pediatrician but they are closed & I called the ER but they told me they couldn't give me any information about what can I do !!