Lesion on my scalp

Hi there.
I'm a 36 year old male, with an olive complexion. I'm bald and use a set of clippers to shave down the areas on my head where hair still grows.

Last week, I noticed a pink, inflamed cluster of bumps. I thought it was razor burn, but the cluster got a little larger over the next couple days and kind of formed into a flattish, raised lesion. Now, the lesion seems to be getting smaller. but I've also noticed it getting slightly scabby and red on spots. The area is somewhat sore and hard to the touch.

I recalled that I had used WD-40 on the clippers before using them (a lubricant I hadn't used on them before) on the day that I noticed the spots. I also went to a public water park that day.  

So, naturally I'm wondering if this is some form of cancer or pre-cancerous growth or if it's just a kind of dermatitis, eczema or psoriasis. I've had little patches of eczema on other parts of my body in the past and have had a few rounds of blepharitis.

Here's an image of the lesion taken today (the small spot in the back/middle of my head has been there forever, I'm referring to the pink spot nearer the front of my head): http://farm4.static.flickr.com/3492/3896414491_e8af3ab21a.jpg