Maybe not even that, he was (is?) snorting his meth. From what I read (and correct me if I'm wrong), while meth isn't as acidic as somethimg like coke, "meth" nose can still onset within a year, maybe even just months.
Like most insufflated substances, it's a function of the inherent ability of the substance to damage the tissues exposed to it as well as the dose/response relationship. The frequency and size of dosage as well as its toxic potency is directly related to the rate and severity of deterioration.
Cocaine and meth both damage the nose in similar ways, but there are some big differences, with meth actually being worse.
The most common salt of cocaine, cocaine hydrochloride, is typically neutral to slightly basic. However, once it is introduced into the nose it hydrolyzes (interacts with the hydrated mucous in the nose) in a reversible reaction to create a hydronium ion (H3O+) that creates an environment that has a pH of 4-5. Interestingly, the acid is a minor contributor to the damage to the nasal passage, probably only 20% or so. It is the incredible sympathomimetic (mimicking molecules that act on the sympathetic aspect of the nervous system, such as adrenaline [epinephrine]) properties of cocaine that cause a sustained and quite strong vasoconstriction of the tissues in the nose, leading to localized ischemia (lack of blood flow), and the tissues die. Since the septum is cartilage and has no major vasculature of its own, it relies on the mucosal tissue to provide it with oxygen, nutrients, and without it the cartilage dies as well.
Meth is actually substantially worse than cocaine in the damage it does to the nasal passages. Meth is typically much "dirtier" than cocaine as far as the crap left behind in it from manufacturing it for street distribution. As a result the chemical burn it causes contributes significantly more to the damage done to the nasal passages, accounting for about 50% of the total damage done. Also, the half-life of cocaine in the nasal passageway is about an hour, give or take, while meth has a 10-12 hour half-life. The time the tissues spend in vasoconstriction is far longer. As such, it would take a much smaller dose of meth, over a much shorter period of time, compared to cocaine, to do the same amount of damage to the nasal tissues.
So, depending on exactly what he is shoving up his nose, and how often he is doing it, substantial damage to peripheral tissues such as the nose may be much closer than further away.
