Rough edges for a solder joint
The jagged edges are not by themselves problems.

However, in this case they indicate bad soldering.  Either the solder never properly wetted everything and didn't flow right, or you heated it too hot for too long so that the surface significantly oxidized.  Your pictures also show excessive use of solder.

Go back, clean off the mess, and use just enough solder.  Add fresh solder, and possibly extra flux.  Make sure the solder flows nicely over everything.  Make sure there is enough solder to hold everything, but not more.  Once the solder flows and wets everything, remove the heat and hold both parts still until the solder hardens.

I'd probably set the iron to 650&deg;F (345&deg;C), or 700&deg;F (370&deg;C) and be sure to hold the iron there only as long as it takes.  I do normal soldering where nothing is particularly large or of unusual material at 600&deg;F.  The reason I say to use a higher temperature here is due to the large pins acting as heat sinks.