Good thing that you already removed the board. The next thing to do is to clean it. You must remove all the EMI shields of the logic board. If you do not remove those you are not cleaning 3/4 of the board. Clean everything with +90% (no less than 90%) isopropyl alcohol. Follow this guide, and even so it was written for an iPhone 3G all the points are still pertinent to your phone. Pay particular attention to the SMD components, check for charred missing or broken components etc.. You can then dry the board in an oven or equivalent at 220deg F (not higher;-) for a few hours. Best way to clean it would of course be through an ultrasonic cleaner. Consider professional help with that When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Once all this is done, reassemble your phone and reevaluate. Only after cleaning your board can you really evaluate what is going on with it. If it has shortened out etc. you will need the schematic for it, posses some testing and repair equipment and need to know how to use all that stuff. Sometimes it’s best to get some extra help from people like @refectio etc. for repairs like this.