Hmmm . . . can't speak to the lumps, but the cracked skin behind the ear is classic eczema. Ds has this (the ears), my brother had it as a baby, and my dr. agreed it's very common. Your dr. will never agree with this, but every single alternative health care provider I've talked with is convinced that eczema is caused by allergies. (trad. medicine says no one knows the cause)
I'm not a health professional, but I would suggest cutting out cow's milk first, and then wheat, and maybe corn to see if you can get them cleared up. I agree that the ears in and of themselves aren't that big a deal, but they could be a warning sign that more widespread eczema is on the way. (or they could be all you ever see!)
I also like Nelson's homeopathic calendula cream -- it works very well for us, and even if it doesn't clear things up, it can help prevent infection for when the cracks bleed (ds's do that, too, esp. when he scratches in his sleep).
Try doing some internet research on eczema, if you're not familiar with it, and maybe even get Is This Your Child by Doris Rapp -- she's a little extreme, seems to think everything is an allergy -- so don't let her freak you out, okay?
Good luck. I hope the red lumps go away -- and feel free to PM me if you need more eczema info or support (there are also a lot of eczema moms here!).