Babies left eye.. Advise please!

Ke

As you can see in this picture when he is really focused on something his left eye turns inward. It doesn’t stay like this hair when he’s really focused on something right in front of him. I didn’t notice this til after his 4 month check up. What should I do?? Eye doc now or wait and bring it up at 6 month check up?? And does anyone have any experience with this!?