What should I do?

Idk if I'd get a new pediatrician, but i would definitely express how that crosses a boundary. How they respond would determine if i get a new one

I wouldn't think anything of it at all.

I dunno. I think it’s all personal preference.
Our paediatrician is lovely and my son likes her. I’d prefer him to feel comfortable, calm and happy whilst he’s at a serious appointment about his health
(Obviously I don’t know what your paediatrician is like!)

I wouldn't like that either. I understand that they probably just love babies which is why they did that, but also as a Dr shouldn't they know that the mouth is filthy?
I still wipe down my baby's hands and feet after leaving public places, but maybe Im just paranoid 😅. But i dont think they should've done that especially since your baby is getting to the stage of sticking their own feet in their mouth.
Do you have any other complaints abt ur pediatrician otherwise? If not I would respectfully ask them to not do that in the future.
But if you aren't that attached to the pediatrician to begin with I would consider switching. But I would at least give them a chance to correct their behavior, or maybe tell them why you're switching so they know not to do that with other patients.

I feel like if they’ve been seeing your baby a while they might feel comfortable but, if YOU feel uncomfortable that’s all that matters. you should just tell them you’d prefer if they didn’t do that and if they start acting weird then get a new pediatrician or if you’re not confident in speaking up just get a new one anyway! it’s all about comfort for you and your little!