I'm not a fan of lip fillers at all, sorry. Every time someone insists that theirs look "totally natural", they never do. The area around the lips always looks thickened and a bit odd.
When you don't know the person, it's less jarring. But as a PP said, when it's someone close to you, or a face you're familiar with, the effect can be a bit of a shock.
I think if DP suddenly rocked up at home having had some fillers injected into his lips, I wouldn't be impressed. Everyone ultimately has body autonomy and it's up to you what you want to do. But in a long term relationship it's totally normal for a partner to have a preference over your appearance. And although you might not think so, lip fillers are quite a striking change especially when they've just been done. That doesn't mean they get to dictate what you look like, but having a preference is normal.
Yes, modern fillers are pretty safe but they're not totally without risk even in the hands of an experienced practitioner. A single slip or bad reaction can leave your lips permanently wonky, lumpy or worse. I don't understand why anyone would risk this - or why they want to look like every other female celebrity. Pumped up lips - to a lesser or greater degree - impossibly smooth foreheads and expressionless faces. It's like a succession of factory-produced similes. And that goes for the men as well as the women.
Absolutely your body, your choice. But your DH is entitled to find it unattractive - I guess the question is, what would you do if your DH changed his appearance in a way that you really, really didn't like and that he couldn't instantly rectify? Would you be happy about it, even though you hated it but he insisted that he loved his new look? Would you be OK with the fact he changed his physical appearance to something that you really don't like without talking it over with you first? Would you be happy that he did something that carries some risk of permanent damage without talking to you first?
I don't know what your relationship dynamic is. No one should have control over another person's body but personally, I'd talk to my DP before doing something like this. When your lips settle down he'll probably get over it.