No response when unplugged, flashes green battery when plugged in

My Huawei P8 Lite is totally unresponsive when it's not plugged in, but when it's plugged in it continuously flashes the little green full-battery symbol and that's it. The charger is also emitting a high-frequency noise when plugged in to the phone which gets slightly louder when the symbol is showing... The charger has been making the noise since I got it, in every power point, but these two problems might be related.

I'd really rather not hard reset my phone, but if it comes down to it obviously I'll have to... Please help!

PS. This has come on incredibly suddenly. I was using the phone at 3am this morning (it's now 10pm), plugged it in, went to bed, and when I woke up at 9am it was in this state.