My son recovered from covid two weeks ago. this morning he spiked a 103 fever. i gave him motrin and it never came back. why would the fever be so short??

I would wonder about an error by the thermometer. Or not taken properly. You did not say how old he was but some have been known to fake a temp to get out of school etc. The most accurate body temp its a fresh urine caught in an insulated cup. If you are using a mercury or similar thermometer they can be heated up by running against cloths or sheets or light bulbs. Discuss with Dr.