As whisperwolf stated, this is not appropriate treatment. The infection may consist of bacteria which are not affected by Ampilox, or moderately affected, so you will develop a resistant strain. In addition the infection in a boil is usually encapsulated. Surgical debridement, which entails lancing and flushing the cavity with saline, often under a local lidocaine anaesthetic, is the treatment of choice, followed by a broad spectrum antibiotic, or ideally, an antibiotic that has been selected based upon a culture of the bacteria. The lancing and flushing are relatively painless, and usually necessary.
I would not use the Ampilox without a prescription from the doctor. If it is the wrong antibiotic for the infection, you could end up with a drug resistant strain.
If it is truly a boil, it will need to be lanced to drain the infection first.