328 exhaust leak

Well...it won't hurt anything to drive it in the short term though it will just get worse so it should be repaired as soon as is convenient.

Looking at the pic and the rust/corrosion shown, be prepared for the repair to more complicated than simply unscrewing the fitting and cleaning up the mating surfaces - it might be heavily seized. The pipe or the exhaust fitting itself could break. If so, absent a careful approach, the simple repair could become a genuine PITA! If it is seriously seized, heat is your best friend!

 

Is the leaking tube clamped to an adjacent port? This will help prevent the tube from coming out of its fitting when it fully fails.
After having issues with my emission exhaust analyzer tubes for rear bank leaking....
I decided to acquire a new set (done), remove the existing rear tubes and install 110860 stainless plugs and copper washer to seal the rear bank header ports. Ordered from Ferrari dealer (Houston). I used nickel based anti-seize when installed.
To remove...
I used multiple applications of PB blaster, time, and heat. I cutoff the leaking tubes and used a socket over the fitting and torque to get it out.
Even used vise grips and small hammer to get it free from the port. The use of mild steel brake lines for the tubes is the Achilles heel. Brass fitting in a stainless port.
The ticking can get loud when the cracking worsens. You will be able to hear it clearly while driving.
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About 10 years ago one of the sniffer tubes on the front header of my 328 GTS broke off near where it fastens to the header. I noticed it from the noise it was making. It had been eaten through by corrosion. I removed the header (much work) but could not get any of the bolts out. I ended up using my Snap On stuck bolt remover to remove all four of them. I plugged the holes with ordinary bolts.