It is difficult to predict exactly whether the fever will completely settle by tomorrow morning, because it depends on the underlying cause of the infection and how your body responds to treatment. Sometimes fever improves within hours after an injection and medicines, while viral or stomach-related infections may take a couple of days to settle. Rest well tonight, drink plenty of fluids/ORS, eat light food, and continue only the medicines prescribed by your doctor. If the fever remains very high, you develop vomiting, severe stomach pain, dehydration, breathing difficulty, or worsening weakness, seek medical care promptly. Prioritize recovery over attending class if you still feel unwell tomorrow.