iPhone 5s battery corrosion?

Hi ! I have a new iPhone 5s, it has less than 40 days. I was charging it, without using it, not exposing it to the sun. When i looked it, i noticed that it was extremely hot. Then, I noticed that it has some kind of drops at the back, like some kind of transpiration for the overheating. I leaved it, to cool it down, and then i noticed that some stains remains on the metal, next to the symbol of the Apple.

My most important doubt if that liquid could be some kind of corrosive liquid that battery leaked through the metal. I didnt touch it, but if the battery is corroed i have to stop using the phone. I dont wanna use any toxic product.

My other problem, it's that there is no official support in my country to let them check the status of the battery, and Iwont be travelling soon to another country; so I really dont know what i can do, when my iPhone is still on warranty.

Any help would be appreciated. Thanks.