1 month Post explant. One breast is larger. Should I be concerned? (photos)

You could have residual swelling present from surgery contributing to the asymmetry. Your surgeon will be able to rule out a seroma with an exam or ultrasound. If the asymmetry becomes worse or you develop pain or other symptoms, reach out to your surgeon for an evaluation.

Without examining you in person, impossible to truly answer your question. My hope is that the asymmetry is simply due to swelling. However, your surgeon should be able to give you a more accurate assessment after examining you in person. Best of luck.

I won't be able to answer your question completely without an exam.
It is typical to have some residual swelling or small seroma this soon after an explantation. For as long as there is no infection (does not appear there is in your photo) the asymmetry will improve as you heal though that is not guaranteed. Your breasts will not look exactly the same as before you were augmented and the mild asymmetry you have is likely expected.
I would recommend massaging the breasts to help all residual swelling or fluid to resolve then follow up with your PS as planned