Hello all, I am a foot health practitioner, and deal with IGTN's on a daily basis. A chiropodist or FHP is much more knowledgeable about this, so visit them first.
The treatment really depends on the severity of the IGTN, so really i can only advise.
If it is quite high up at the side of the nail and there is no infection or hypergranulation (red, swollen area of tissue), packing may be possible. This is where a small, rolled piece of cotton wool is eased under the free edge if the nail, and eased down the side of the nail as well, then sticks out at the side of the nail, therefore lifting the offending bit of nail away from the skin.
If there is infection or hypergranulation, you will need antibiotics as well, so get yourself off to the gp.
If the IGTN is low down the side of the nail, a chiropodist will remove the offending bit, or suggest a permanent solution to the problem, which is a partial nail avulsion, where the side of the nail is permanently removed.
Sometimes if the nail is involuted ie curved around in a 'c' shape as you look from the top, a nail brace may be used. This is where wire is stuck at the bottom of the nail, where it stays until the nail grows out. The wire pulls the nail straighter. Sometimes a plastic (or gold, Mrs B) strip is used instead. This works, but takes a long time!
As a rule, toenails should be trimmed straight across. If you start cutting down the sides, you risk leaving a piece behind which may dig in and cause an IGTN. A chiropodist may trim down the sides, but remember, they know what they are doing and have a much better view than you.
If you are diabetic, an IGTN should be dealt with asap. Diabetes effects the body in several different ways, but concerning this, it can impair the immune system, so if an infection gets in, the body cannot rid itself of it. This may eventually lead to ulceration, and in the worst cases, amputation. Also, diabetics sometimes suffer from neuropathy, with is some level of lack of sensation in the feet. Therefore the may not FEEL an IGTN, thus leading to infection, ulceration, etc.
Diabetics, PLEASE look after you feet! Camille, if you are diabetic, please let a professional deal with it. NO digging down the sides!