I can not get the bypass cap closer as it would make the PCB too wide to fit in many places where the Nano does. The PCB is already too wide as it is, because the DIP-28 chip takes up most of the space. I could add a spot on the underside for the bypass cap for those who have the clearance on their PCB for it, but for breadboard use the capacitor would stick out from the bottom. The trace distance between the capacitor terminal and the 5V terminal is about 8 mm which is not ideal but should be OK, about 50 nH or about 15 ohms at the 3rd harmonic of the clock frequency (48 MHz).
While it would be better to put the crystal closer to the pins, the inductance of the lines is very small compare to the effective inductance for the high Q crystal, and the capacitance of the extra length of traces is in the sub-pF range. Again, placing it on the bottom side would make it unusable for a breadboard.
I stitched up the top and bottom with vias because the vias are basically free when you're ordering small quantity and it helps with EMC/susceptibility. I don't expect the EMC performance to be great but at least I can try.
Given that the ATMEGA328P is regularly assembled on a breadboard and generally works, the I am not overly concerned about having a bypass capacitor a few extra mm from the power pin.
Digikey has got 1813 pieces of ATMEGA328PB-AN (TQFP32) on stock at the time of composing this text.
The layout of your PCB shows clear signs of a beginner's work. That's not a bad thing since we all started doing things at some time, but you should be aware of them:
1. The bypass caps need to be directly at the VCC-GND pin as near as possible to be effective. Even when using a DIL uC SMD caps would have been much better from an electrical point of view.
2. Same is true for the crystal. Although your design may work choosing SMD parts would have made your design more reliable since trace length could have been smaller.
3. A LM7805 is really old and has 2 volt dropout voltage. If you would use an MCP1702 your design would still work at 6V input voltage with 5V output voltage.
fchk