This could come from a leak at the drain plug; either because the plug was not tightened securely, or it was cross threaded; or the sealing washer was left off or was damaged, or the pan was damaged. The other possibilities are that the oil pan bolts are loose, or there is a leak from the valve cover, the timing cover, or the oil filter, or somewhere on a higher part of the engine which is running down the side and dripping off the lowest spot on the oil pan. Oil leaks generally come from the highest point on the motor that has oil on it. If you cannot locate the source of the oil; have the motor steam cleaned or pressure washed; so it will be easy to see where the new oil leakage comes from.
If your Altima has the 4 cylinder motor; you should be aware that there might be an internal engine problem which causes excessive pressure to build up in the crankcase, and causes leaks at gaskets and seals. This kind of excessive pressure will push past oil seals which are in good condition; so it is not possible to stop it. Around the time this car was made; Nissan issued an order to all its dealerships, for them to stop selling 4 cylinder Altimas until they redesigned the engine to stop the oil consumption problem. Many of these vehicles were consuming so much oil that it was causing the catalytic converter to clog up and overheat; which created a danger of fire. To the best of my knowledge; nobody has been able to correct this problem by rebuilding the engine, replacing pistons, rings, or valve seals. The factory redesign went beyond the usual repairs; I think they probably changed the materials and tolerances used in some of the critical parts.
I hope your car does not have this problem, and is just leaking from the drain plug.