Hi,
Welcome to the forum. I am really glad to help you out. This is called parosmia.
It is hypothesized that URTIs (upper respiratory tract infections) can result in parosmia because of damage to olfactory receptors. Exposure to harmful solvents has also been linked to parosmia. Damage to these neurons could end in the inability to correctly encode a signal representing a particular odor, which would send an erroneous signal to the odor processing center, the olfactory bulb.
In humans, the olfactory bulb is located on the inferior side of the brain. Physical damage (head injury) to this area would alter how the area processes information in a variety of ways. If the part of the brain that interprets these input signals is damaged, then a distorted output is possible. This would also lead to parosmia. Please do consult an ENT surgeon for the same. I sincerely hope that helps. Take care.