Black spot under the skin could be blood blisters from mites...as Opus wrote, hard to tell from a description.
I'm sorry I must strongly DISAGREE with the first post DO NOT use water nor a turkey baster ever in a cats ears....PLZ see a vet, still sounds like mites but hard to tell without a visual.
You can clean with a cotton ball dipped in dab of olive oil and see if that helps, but won't if under the skin...vet is best:(
You can use warm water and a bit of dish soap to wash the ears out. Make sure you rinse well to get ALL th soap out. You might want to trim the points off Ginger's nails first. This procedure only takes a couple if minutes, and can be done in your kitchen sink. No, water in cat's ears does not harm them in any way, ut you do want to get that soap out. Dry gently with a towel. If Ginger shows any signs of actual pain (like when you rub her ears, she goes crazy), then stop. Call your vet and get an appointment - it will be easier for the vet to asess her hears if they are clean first anyway. Sidenote: a turkey baster is a good tool for cleaning ears. :)