I've read a few posts about samsung S7 USB chargers melted into the phone, unfortuntly I've had the same/similar only mine seems worse, the entire mini-usb-cable-plug melted and although the phone initally powered on it will no longer charge at all or power on. 😞 the Mini-USB connected was melted and was a pig to remove from the phone. (I am wondering if this is a common fault)
Are you based in the UK or Ireland? And have you been in touch with the Support team or a local Support centre about this? If you haven't, can you send me a PM with your details and I'll forward them on to my colleagues for them to contact you ASAP.