Antibiotics are medications that are effective in treating bacterial infections. Many common problems, including coughs, colds and sore throats, are usually caused by viruses. Antibiotics don't work against viruses. In addition, many common bacterial infections get better by themselves without needing antibiotics.
Taking antibiotics when you do not need them can cause bacteria that normally live inside you to become resistant to these drugs, leading to the potential for severe infections in the future that may be difficult to treat. Antibiotics also have common side effects including nausea and diarrhoea.
If your GP has not prescribed you antibiotics, they will have discussed with you what to watch for, and when you might need to be reassessed if your problem is not improving.