Is it permissible to accept financial aid provided by the Ministry of Social Affairs to an individual suffering from social phobia, whom the medical committee affiliated with the Ministry has deemed unable to work?

There is no deception or trickery in the procedures you undertook to obtain the assistance, and therefore there is no blame upon you in benefiting from it as long as you are in your current condition. However, if you recover and the ailment leaves you, then you are obligated to inform the entity providing the assistance of that.