Is The Brain Lesion Shown In The MRI Something Serious?

hi. i have been having on and off headaches for the past 3 weeks (esp on the left side). sometimes it comes with fever, flu and the urge to vomit. and sometimes it comes with neck and knee joint paint. i've done MRI and according to the result there's nothing wrong with my brain except there's white lesion on the left side. please help. issit something serious?