The club had looked for a six month loan but Charlton boss Alan Pardew has said he would assess the situation after the initial one month spell.
Dickson will go straight in to the squad for the away trip to Bristol Rovers and will wear the number 31 shirt.
22-year-old Dickson signed for the Addicks in March of this year for a fee of £35k rising to £50k. His goal scoring exploits at Dulwich caught the eye of the management team at the Valley and the club acted swiftly to ensure they signed him up.