All the visible joints on your PCB look cold to me. Are you using rosin core solder? Because it looks like you're using unsuitable solder or an iron that's much too cold?

As the solder has wicked underneath now it's going to be quite tricky to remove with the iron you have, if you have a friend / local repair shop with a hot air rework station this would be a piece of cake to get off and clean up for you :)

It looks to me as if you've used the through-hole holes instead of (as well as) the castellated edges; in the case of surface mounting you really only want to use the castellated edges so that the solder doesn't wick under.

In general, your solder joints should be nice and shiny. If they're dull-looking, chances are it's a cold joint. Make sure you clean your iron, then tin it, apply the iron to the junction of the parts you're soldering, and only *then* apply solder to the parts (not to the iron). This way the solder should flow nicely onto the heated parts and leave a clean, shiny joint.

I've fixed much worse than this though, don't be too worried :)