I Know This Is A Random Question But My Parents

I know this is a random question but my parents are out of town, I am keeping my sisters and the 5 year old one is burning up hot, The only thermometer I have is the ear one and it keeps bouncing from 100.2-98.7 then to 99.9. Should I be worried? The one thing I don't have here is medicine for a fever, so I'm panicking. She has been herself all day and night but she started coughing and I gave her some cough syrup and noticed her cheeks were a little red so I felt her head and thats when I checked her temperature. Sorry to bug you!