These vocal nodules you have mentioned are non-cancerous growths on both vocal cords caused by vocal abuse. They appear because of vocal injury without rest. First you get blisters. If you take rest, these blisters will go away. If you don't give rest, then these blisters become firm and callous. Usually symptoms are based on patient s vocal demands. In your case. You may get hoarseness, inability to sing quietly and hold a pitch steady. There may be feeling worn, discomfort, pain, and tightness. Hoarseness is an early symptom to evaluate whether it is reversible or not. In your case you have mentioned that you do not have a hoarse voice. If you take enough precautions for your vocal hygiene, then nodules are preventable. You also mentioned that you have a sinus problem. These vocal nodules are not connected with sinus problem. They are a different entity altogether. You can treat the voice nodules by taking a few steps such as:

a) Complete voice rest should be done and use of anti-inflammatory drugs like ibuprofen twice a day for a week can be given to reduce the swelling.

b) Voice therapy will make the nodules softer, more flexible and also improve the voice.

c) Good vocal care.

d) Avid use of irritants, shouting or excessive clearing of throat

e) Hydrate the body well and use steam inhalation

f) If all methods fail, then it may require surgery.

Try this for 2 weeks; if you see no signs of improvement then you consult an ENT surgeon for further evaluation.