My little one is 4 in a half month old and she has a common cold with a temp of 100.04 should i be concerned?

NO,most of the time: but some times it may not be common cold , only the pediatric evaluation will clear , take child to the doctor, then you don't have to worry.

This is normal: Your infant has what's considered a low grade fever. Most fevers are good for sick children and help the body fight infection. Fevers only need to be treated with Tylenol (acetaminophen) if they cause discomfort. That usually means fevers above 102°F. Call your doctor if fever lasts more than 72 hours, or signs of dehydration (no wet diapers in 8 hours, crying with no tears, sunken eyes or soft spot).