How much current can a solder joint carry?
If the trace/pad is sized correctly and you aren't shoving more current through the pin than the component designer intended (assuming they sized the pin appropriately for their part) you don't need to worry in most situations. The solder has much more cross sectional and contact area with the pad and pin than the trace cross section.
I wouldn't worry unless you are running in very hot ambient temperatures or running extremely high currents (50A? 100A? maybe not even then) and if you do, using silver solder increases conductivity by 2-4x which will probably get you out of it if you didn't bungle things too badly.