My big beef has little black spots????

[SunKissed]

I have a 1.25' big beef tomato plant and i found little black spots forming on the bottom leaves. I dont see any caterpillers plus there are no holes and i dont think its blite because theyre super small spots and very dark. It's also only on one side. I wonder if when i watered the plant the sun burned it..? any ideas? Also, do i leave the yellow flowers on the plant or take them off? I'm a virgin gardener...totally in the dark w everything :)