with yellow crust is likely a skin infection
(staphylococcal) and the tumefaction along the hairline is due to inflammation of lymph
node in response to the infection. The child will be well. You may not need a specialist consultation; antibiotic and analgesia/antipyretic
will do. This can be prescribed by a pharmacist, nurse or GP and the child should be fine with these. My advise is that you consult for treatment to be started soon. If you have any pain killer or antipyric you can start given the child. Watch out for fever
as this indicate dissemination of the infection. So start antibiotic soon without waiting till Monday.
Hope this is helpful