First time mom screaming for help

My 4 month old son is EBF.

Occasionally I let my mother in law watch him for a couple hours so I can do homework etc. About a week ago she told me she gave him a Gerber Puff and he was sucking on it but she didn’t know where it went. For the past week now he’s been coughing. I thought it was due to a cold he had and all the mucus was in his throat and he was trying to cough it up. But he spit up a little bit earlier during his coughing and this came out. I honestly have no idea what it is. But it does smell like a strawberry puff. I’m too scared to talk to her because she takes everything to heart and she’ll play the “well you don’t trust me with your son” card.

What should I do !!!?? Should I just let him spit it up naturally or taking him to the ER?