The most accurate way to diagnose and accurately treat your condition would be with a biopsy of the nail and skin.

It could be fungal infection. We send the nail to the lab to determine if it is indeed fungal. In the meantime can use the tree oil or Vicks vapor

Most common cause for nail changes is micro trauma and nail fungus. Both are treatable with good results and 75% cure rate with traditional treatments. We use advanced fungal therapy to increase cure rates to 85-90%.

It's crucial to address these symptoms promptly. Dr. Jose Loor is here to provide the expert care you need. Yellowing, blackening, and thickening of nails, along with the formation of pimples, could indicate an underlying issue that requires professional attention.

To ensure the best care and diagnosis, I strongly recommend booking an appointment with Dr. Jose Loor. You can schedule your visit at joseloorpodiatry.com or call (646) 631-8861.

Your history of nail color changes suggest that you are developing microtrauma to the toenails possibly from wearing tight-fitting shoes such that they are either too narrow or too short. In terms of what can cause this, the two most common reasons are microtrauma and nail fungus. The only definitive way to differentiate between the two is to get a nail biopsy from a podiatrist.
In the event this is microtrauma, the dark discoloration may be dried blood under the nail that will naturally grow out with the nail. The typical timeframe for the nail to grow out from the cuticle area is about 9-12mo. I would suggest taking pictures every 2-3mo to track the outgrowth.
If there is any pain associated with this, then I would get it checked out sooner with your podiatrist.

You appear to have fungus in your nails. Oral antifungal works the best, but has possible side effects. Topical antifungal is safer, but doesnt work as well as the oral. I would recommend making an appointment with your local podiatrist so he can discuss with you the best treatment for you.

The changing thickness and coloration of toenails can come from either trauma or toenail infection. Sometimes systemic conditions such as psoriasis can affect toenails as well. I would recommend that you see a specialist, and have a biopsy/specimen of the toenail and sent to pathology to see what is the cause of the thickening of the toenail. At that time treatment plan can be started. Once causative condition is known. Jonathan M. Kletz, DPM Texas Foot WorksDallas, Athens and Gun Barrel City Texas214-340-8885

There are many causes for toenail discoloration and thickening. I would contact a local physician for assessment and treatment options.
There are also many causes to rashes on skin, I would recommend being assessed by a local physician!