If this discolouration is associated with the lifting of a nail coating from the nail plate it is probably ‘greenies’ or chloronychia all of which are a bacterial infection of Pseudomonas. Consulte el artículo completo sobre la enfermedad cloroniquia
Tratamiento y recubrimiento adecuados tras una infección de las uñas
In any case, the way to go is to remove the coating and seek medical advice. Once a correct diagnosis has been established, then a range of therapies are available which include avoidance of moisture, topical acetic acid/hypochlorite soaks (vinegar/bleach), antibiotics, and others.
The doctor will be able to prescribe the most suitable one. Only apply a new coating once the treatment has been successful, the infection detained, and the “greenie” has grown out.
Spanish 
English 
Portuguese 
Vietnamese