one time incident with my big dog

hello everyone! I need advice on what to do about an encounter we just had with another person.

for some backstory - my dog is a very large breed (he is 190lbs), but he is a gentle giant. he is almost 10 years old. he has never barked at anyone or been aggressive in the past. he has met 5 people in our building so far. all of them have complimented on how sweet and gentle he is for being such a big boy. I understand the stereotypes associated with dogs his size, and if I didn’t know him myself, I would also be reserved around him.

today I took him outside for a bathroom break, and as we were coming inside there was a very small woman coming off the elevator. we could both instantly sense the fear in her. my dog reacted by barking at her, she then started screaming and ran away. I think this was him protecting me because he felt something was off. he calmed down after she was out of sight, but a woman in her room popped out and yelled at me to muzzle my dog.

again, this is a one off issue. I am worried about a muzzle as I believe it may cause more fear from those who typically wouldn’t be scared because muzzles (in my head) are associated with aggression. I have two questions that I need advice on. will a muzzle plus his size lead to bigger issues with this? or is a muzzle a good idea and I need to leave my own opinions and feelings aside? I feel horrible that he scared someone and i’ve been so guilty all day. thank you for your time and input<3 we really appreciate it!

edit: I am very capable of controlling him or holding him back if/when necessary. i’ve held him back from running too fast or running at another dog many times. he also is extremely well behaved. he usually just looks at someone when they walk past or saunters up to them and wants attention. behaviour like this (or any other negative behaviour) has never been an issue.